Reflection-type digital phase shifter

ABSTRACT

A reflection-type digital phase shifter, which may also be called a path length modulator is disclosed comprising a waveguide, a pair of diodes interconnecting first and second opposite walls of the waveguide, and a center conductor of a coaxial cable extending through a third wall of the waveguide to bias the diodes.

United States Patent inventors Mark R. Barber Summit; Reed E. Fisher,Parsippany-Troy Hills Township, Morris County, both oi NJ. Appl. No.858,229 Filed Aug. 4, 1969 Patented Dec. 21, 1971 Assignee BellTelephone Laboratories Incorporated 1 Murray Hill, NJ.

Original application Feb. 23, 1966, Ser. No. 529,453, now Patent No.3,460,122, dated Aug. 5, 1969. Divided and this application Aug. 4,1969, Ser. No. 858,229

REFLECTION-TYPE DIGITAL PHASE SHIFTER 9 Claims, 2 Drawing Figs.

, 333/73 W, 333/98 1nt.Cl li03h 7/18 Field oiSearch 333/3i,7,

References Cited UNITED STATES PATENTS Thomas"; Morrison. De Poy HinesMunushian Peppiatt Koueiter.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-C. BaraffAttorney-R. .1. (iuenther and ArthurJ. Torsiglieri ABSTRACT: Areflection-type digital phase shifter, which may also be called a pathlength modulator is disclosed comprising a waveguide, a pair of diodesinterconnecting first and second opposite walls of the waveguide, and acenter conductor of a coaxial cable extending through a third wall ofthe waveguide to bias the diodes.

REFLECTION-TYPE DIGITAL PHASE SHIFTER This application is a division ofUS. Pat. application Ser. No. 529,453, filed Feb. 23, 1966, which issuedas US. Pat. No. 3,460,122 on Aug. 5, 1969. This application incorporatesessential material contained in U.S. Pat. No. 3,460,122. US. Pat. No.3,460,122 describes apparatus for converting analog voltage signals tovoltage binary digits representative of such signals. A part of thisA-to-D apparatus is a reflection-type digital phase shifter. Thisdigital phase shifter is the subject of this application.

The digital phase shifter comprises a wave guide, opposite walls ofwhich are interconnected by a pair of diodes. The diodes are biased by asignal produced in the A-to-D converter and applied to the diodes by theinner conductor of a coaxial cable that extends through an end wall inthe waveguide. The diode characteristics are arranged with respect tothe waveguide characteristics such that when the diodes are biased inone direction they are at series resonance and hence constitute avirtual short circuit across the waveguide. When they are biased in theopposite direction, the diodes form a parallel resonance with the endwall of the waveguide and constitute a virtual open circuit. Thewaveguide is preferably rectangular and transmits carrier energy in aTE, mode while the coaxial cable transmits diode bias energy in the TEMmode. With proper coaxial cable dimensions as will be explained later,the TE, carrier energy is restricted to the waveguide and cannot betransmitted by the cable. When the diodes are biased to obtain parallelresonance they will shift the phase by 180 with respect to the phaseshift obtained at series resonance. Since the diode bias changes only inresponse to a changed phase of the input to the stage, the carrieroutput of the phase shifter is of a constant phase regardless ofthecarrier input phase.

These and other objects and features of the invention will be more fullyunderstood from a consideration of the following detailed description,taken in conjunction with the accompanying drawing in which:

HO. 1 is a schematic cross-sectional view of a preferred embodiment ofthe digital phase shifter; and

FIG. 2 is a view taken along lines 2-2 of FIG. 1.

A digital phase shifter 31 is shown in FIGS. 1 and 2. This devicecomprises a rectangular waveguide 37, a coaxial cable 38, and a pair ofhigh-speed diodes 39. Waveguide 37 is connected to a circulator 32 inFIG. 4 of US. Pat. No. 3,460,122 and a cable 38 is connected to alow-pass filter 29 in the same figure. Connected across the rectangularwaveguide are the pair of high-speed diodes 39, preferably Shottkybarrier hot carrier) or other varieties of low-minority carrier storagevaractor diodes. The diodes 39 are connected to an inner conductor 40 ofthe coaxial cable 38 which extends through an end wall 41 of therectangular waveguide. The outer conductor 43 of the coaxial cable 38 isdirectly connected to the end wall 41 of the waveguide.

The inner conductor 40 forward biases or reverse biases the diodes 39depending upon whether a digital voltage E applied by coaxial cable 38is of the positive or negative polarity. When the diodes 39 are reversebiased due to a negative volt age E their series capacitance and seriesinductance are adjusted to be at series resonance. Waveguide stubs 44are included on the upper and lower walls of the waveguide 37 forproviding an appropriate length 1, for giving series resonance atreverse bias. The series resonance results in a virtual short circuitacross the waveguide plane that includes diodes 39 so that a carrierenergy E, applied by waveguide 37 is reflected back to the circulator asE, with, for example, phase shift. The length 1 between the diodes andthe waveguide end wall 41 is adjusted so that when the diodes areforward biased the waveguide section of length l,, forms a capacitancethat is in parallel resonance with the inductance of the diodes. Thisresults in a virtual open circuit at the plane of the diodes and gives arelative 180 phase shift to the incoming carrier energy. Hence, E, isshifted by 1r radians with respect to E, when the diodes 39 are forwardbiased.

The rectangular waveguide 37 propagates energy in a TE, mode so that theelectric field vectors e, extend between the upper and lower waveguidewalls. The electric field vectors e; of the coaxial cable, on the otherhand, extend radially from the central conductor 40 to the outerconductor 43 of the cable. Transmission of e is similar to strip linepropagation in the region in which vectors e extend from the centralconductor 40 to the upper and lower walls of the waveguide. Because ofthese different modes of propagation, the waveguide carrier energycannot propagate into the coaxial cable and the coaxial cable energycannot propagate into the waveguide. However, the characteristicimpedance of the strip line portion to the fields e should besubstantially equal to the characteristic impedance of the coaxial cablefor efficient transmission of E, to the diodes. Because all of theenergy transmitted within the device 31 propagates as wave energy,spurious reactances are minimized, and the digital phase shifter iscapable of operating at extremely high speeds.

The specific structure disclosed herein is presented only for purpose ofillustration. Various other modifications and embodiments may beemployed by those skilled in the art without departing from the spiritand scope of the invention.

What is claimed is:

1. A digital phase shifter comprising:

a waveguide having an end wall for controllably reflecting wave energyfrom a source;

an interconnection extending between top and bottom walls of thewaveguide and including at least two diodes;

means for biasing said diodes in either a first or a second directioncomprising a coaxial cable having an outer conductor connected to theend wall and an inner conductor extending through an aperture in the endwall and contacting the diodes;

one diode being located between the top waveguide wall and the innerconductor and the second diode being located between the bottomwaveguide wall and the inner conductor, both of said diodes being biasedin the forward direction in response to a first voltage on the innerconductor and in a reverse direction in response to a second voltage onthe inner conductor;

said top and bottom walls including waveguide stubs in which saidinterconnection is connected for giving an appropriate interconnectionlength and thereby placing the diodes at series resonance when they arereversed biased; and

said diodes being located at an appropriate distance from the end wallfor placing the diodes at parallel resonance with the end wallcapacitance when the diodes are forward biased.

2. A digital phase shifter comprising:

a portion of a waveguide having first and second walls that areapproximately parallel to each other and a third wall connecting saidfirst and second walls and defining a cavity therebetween, saidwaveguide being adapted for a propagation of electromagnetic waveshaving an electric vector that is approximately perpendicular to saidfirst and second walls;

a coaxial cable comprising an outer conductor and an inner conductor,said outer conductor abutting upon and being connected to said thirdwall of the waveguide and a portion of said inner conductor extendinginto the cavity through an aperture in the third wall; and

an interconnection extending between first and second walls of thewaveguide and including one diode located between the first wall of thewaveguide and the portion of the inner conductor of the coaxial cablethat extends through the aperture in the third wall of the waveguide anda second diode located between the second wall of the waveguide and saidinner conductor, said interconnection being at series resonance whenboth diodes are biased in a first direction and at parallel resonancewhen both diodes are biased in the opposite direction, whereby waveenergy is reflected with a phase difference at one diode bias withrespect to energy reflected at the op posite diode bias,

3. The digital phase shifter of claim 2 wherein both of said diodes arebiased in the forward direction in response to a first voltage on theinner conductor and in the reverse direction in response to a secondvoltage on the inner conductor.

4. The digital phase shifter of claim 3 wherein:

said first and said second walls include waveguide stubs at which saidinterconnection is connected for giving an appropriate interconnectionlength and thereby placing the diodes at series resonance when they arereverse biased; and

the diodes are located at an appropriate distance from an end wall thatis part of the third wall of the waveguide for placing the diodes whenthey are forward biased in parallel resonance with the capacitance ofthat part of the waveguide between the diodes and the end wall.

57 The digital phase shifter of claim 2 wherein the waveguide propagateswave energy in a mode characterized by electric field vectors thatextend between the first and second waveguide walls while the coaxialcable propagates said bias energy in a mode characterized by fieldvectors that extend radially from the inner conductor, whereby said waveenergy is substantially restricted to the waveguide and the bias energyis substantially precluded from propagating beyond said interconnection6. The digital phase shifter of claim 2 wherein:

the portion of the waveguide through which the inner conductor of thecoaxial cable extends substantially forms with the inner conductor astrip line portion along which bias energy propagates from the coaxialcable to the diode, and

the characteristic impedance of the strip line portion is substantiallyequal to that of the coaxial cable.

7. A digital phase shifter comprising:

a waveguide having an end wall for controllably reflecting wave energyfrom a source,

a first major surface of said end wall being on the inside of saidwaveguide and a second major surface being on the outside of saidwaveguide;

an interconnection extending between opposite points of the waveguideand including at least two diodes;

84 The digital phase shifter of claim 7 wherein both of said diodes arebiased in the forward direction in response to a first voltage on theinner conductor and a reverse direction in response to a second voltageon the inner conductor.

9. The digital phase shifter of claim 8 wherein:

said waveguide includes waveguide stubs to which said interconnection isconnected for giving an appropriate interconnection length and therebyplacing the diodes at series resonance when they are reversed biased;and

the diodes are located at an appropriate distance from the end wall forplacing the diodes when they are forward biased at parallel resonancewith the capacitance of that part of the waveguide between the diodesand the end wall.

I. UNITED STATES PATENT OFFICE CERTIFICATE OF .CQRRECTION Patent No a 629 739 Datedw Mark". lit Barber; Reed E. Fisher- It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Claim 7', continue as follows:

-means for biasing said diodes in either a first or second directioncomprising a coaxial cable having an outer conductor abutting upon thesecond major surface of the end wall and an inner conductor extendingthrough an aperture in the end wall and contacting one diode locatedbetween one point on the waveguide and the inner conductor and a seconddiode located between the opposite point on the waveguide and the innerconductor;

said interconnection being at series resonance when the diodes arebiased in the first direction and in parallel resonance when thediodesare biased in the second direction, whereby the wave energy is reflectedwith a 180 degree phase difference at one diode bias with respect toenergy reflected at the opposite diode bias.-.

Signed and sealed this 30th day of May 1972.

(SEAL) Attest:

EDWARD M.-FLL.'TCHER ,J'R. ROBERT GOTTSCHALK AttestingvOfficerCommissioner of Patents I FORM PO-1050 H0- USCOMM-DC 60376-P69 U.S.GOVERNMENT PRINTING OFFICE: 1969 0-368-334

1. A digital phase shifter comprising: a waveguide having an end wallfor controllably reflecting wave energy from a source; aninterconnection extending between top and bottom walls of the waveguideand including at least two diodes; means for biasing said diodes ineither a first or a second direction comprising a coaxial cable havingan outer conductor connected to the end wall and an inner conductorextending through an aperture in the end wall and contacting the diodes;one diode being located between the top waveguide wall and the innerconductor and the second diode being located between the bottomwaveguide wall and the inner conductor, both of said diodes being biasedin the forward direction in response to a first voltage on the innerconductor and in a reverse direction in response to a second voltage onthe inner conductor; said top and bottom walls including waveguide stubsin which said interconnection is connected for giVing an appropriateinterconnection length and thereby placing the diodes at seriesresonance when they are reversed biased; and said diodes being locatedat an appropriate distance from the end wall for placing the diodes atparallel resonance with the end wall capacitance when the diodes areforward biased.
 2. A digital phase shifter comprising: a portion of awaveguide having first and second walls that are approximately parallelto each other and a third wall connecting said first and second wallsand defining a cavity therebetween, said waveguide being adapted for apropagation of electromagnetic waves having an electric vector that isapproximately perpendicular to said first and second walls; a coaxialcable comprising an outer conductor and an inner conductor, said outerconductor abutting upon and being connected to said third wall of thewaveguide and a portion of said inner conductor extending into thecavity through an aperture in the third wall; and an interconnectionextending between first and second walls of the waveguide and includingone diode located between the first wall of the waveguide and theportion of the inner conductor of the coaxial cable that extends throughthe aperture in the third wall of the waveguide and a second diodelocated between the second wall of the waveguide and said innerconductor, said interconnection being at series resonance when bothdiodes are biased in a first direction and at parallel resonance whenboth diodes are biased in the opposite direction, whereby wave energy isreflected with a 180* phase difference at one diode bias with respect toenergy reflected at the opposite diode bias.
 3. The digital phaseshifter of claim 2 wherein both of said diodes are biased in the forwarddirection in response to a first voltage on the inner conductor and inthe reverse direction in response to a second voltage on the innerconductor.
 4. The digital phase shifter of claim 3 wherein: said firstand said second walls include waveguide stubs at which saidinterconnection is connected for giving an appropriate interconnectionlength and thereby placing the diodes at series resonance when they arereverse biased; and the diodes are located at an appropriate distancefrom an end wall that is part of the third wall of the waveguide forplacing the diodes when they are forward biased in parallel resonancewith the capacitance of that part of the waveguide between the diodesand the end wall.
 5. The digital phase shifter of claim 2 wherein thewaveguide propagates wave energy in a mode characterized by electricfield vectors that extend between the first and second waveguide wallswhile the coaxial cable propagates said bias energy in a modecharacterized by field vectors that extend radially from the innerconductor, whereby said wave energy is substantially restricted to thewaveguide and the bias energy is substantially precluded frompropagating beyond said interconnection.
 6. The digital phase shifter ofclaim 2 wherein: the portion of the waveguide through which the innerconductor of the coaxial cable extends substantially forms with theinner conductor a strip line portion along which bias energy propagatesfrom the coaxial cable to the diode, and the characteristic impedance ofthe strip line portion is substantially equal to that of the coaxialcable.
 7. A digital phase shifter comprising: a waveguide having an endwall for controllably reflecting wave energy from a source, a firstmajor surface of said end wall being on the inside of said waveguide anda second major surface being on the outside of said waveguide; aninterconnection extending between opposite points of the waveguide andincluding at least two diodes;
 8. The digital phase shifter of claim 7wherein both of said diodes are biased in the forward direction inresponse to a first voltage on the inner conductor and a reversedirection in response to a second voltage on the inneR conductor.
 9. Thedigital phase shifter of claim 8 wherein: said waveguide includeswaveguide stubs to which said interconnection is connected for giving anappropriate interconnection length and thereby placing the diodes atseries resonance when they are reversed biased; and the diodes arelocated at an appropriate distance from the end wall for placing thediodes when they are forward biased at parallel resonance with thecapacitance of that part of the waveguide between the diodes and the endwall.